Academic literature on the topic 'Thermal and hydric condtions'

This study aims to analyze the maturation and dispersal of Eugenia pyriformis Cambess. seeds produced in different years, and the influence of variation in thermal and hydric environment on seed physical and physiological characteristics at dispersal. Fruits at different developmental stages were harvested in the city of São Paulo between 2003 and 2010, as well as in the cities of Campinas and Lavras, in 2009 and 2010 and analyzed for size and color. The seeds were extracted from the fruits and their dry mass, water content, germination and vigor were assessed. Results showed that seed maturation is unsynchronized to the maturation of the fruit, taking 45 days on average (430 growing degree-days), longer in rainy times or lower temperatures. Seeds with higher physiological quality were produced in rainy years and when the temperature range was larger. We concluded therefore that hydric and thermal environmental variations during development influence the maturation of Eugenia pyriformis seeds and are able to determine the formation cycle and the final seed quality.

A cultivar of sedum was used in this experience. Stems were harvested from normally developed plants and were exposed to extreme conditions of temperature and draught. Results show that the plants lost significant quantities of water by physiological processes from one day to another, their weight varying from 16.8 g to 47.9 g.

The water distribution into stone specimens in laboratory conditions is evaluated through the infrared thermography method (IRT). Porous building stones samples (calcarenite and sandstone) are examined under stable laboratory conditions (controlled temperature and relative humidity) in order to simulate the same hydric behavior in real scale of material systems <em>in situ.</em> Hydric tests monitored through IRT are performed in order to analyze the capillary water absorption and evaporation transport phenomena into stone samples. IRT technique allows to record thermal images at different intervals of time highlighting the internal capillary and evaporation rise heights, responsible for the majority of decay processes occurring in masonries. The geometric shape of the damped area and the time of spreading are directly related to the open porosity of the investigated stone materials. Hydric tests are repeated for each splitting plane of the specimens (faces), in order to obtain useful results that could be applied for real masonries. Results demonstrate the usefulness of IRT as a non-destructive and portable technique in the field of new construction and for restoration purposes, as well as its importance in characterizing the physical stone features and the effectiveness of applied conservation treatments.

The global objective of this work was to manufacture resistant and durable (water resistant) earth renders with good thermal insulation. For this purpose, a medium plastic clayey soil from Kôdéni (Burkina Faso), constituted by kaolinite (62 wt.%), quartz (31 wt.%), and goethite (2 wt.%), was mixed with dolomitic lime (up to 6 wt.%) to manufacture earth renders. The mineralogical, microstructural, and chemical characteristics of dolomitic lime, as well as the physical (linear shrinkage, apparent density, and accessible porosity), hydric (water absorption test by capillarity and spray test), thermal (thermal conductivity), and mechanical (abrasion resistance, flexural, and compressive strengths) properties of the earth renders were evaluated. From these studies, it appears that the addition of dolomitic lime induces the formation of calcium silicate (CSH) and magnesium silicate (MSH) hydrates. These CSH and MSH are mainly formed from the pozzolanic reaction between finely ground quartz and the weak silica of kaolinite in basic media. These formed hydrates improve the physical, hydric, thermal, and mechanical properties of earth renders. This improvement is due to the fact that the formed CSH and MSH stick to the isolated particles of the soil, making them more compact. In view of the good mechanical strength and water resistance, as well as the low thermal conductivity, the elaborated earth renders are suitable for habitats with dry climates, such as the Sahel.

In order to meet consumption requirements, according to the crops destination and way of preparing the fruits, the eggplant breeding process aims at obtaining some cultivars properly adapted to the climate and soil conditions from different culture areas. Â In this context, the selection of genotypes which are tolerant to the thermal and hydric stress represents a major objective of the eggplant breeding.

Les marais de l'Ouest ont été gagnés sur les sédiments fluvio-marins par poldérisation débutée dès le moyen âge. Les aménagements hydrauliques avaient, initialement, des objectifs sanitaires et d'élevage. A partir des endiguements, ils ont divisé les territoires en marais mouillés et marais desséchés. Depuis les années 1970 le développement des cultures intensives de céréales a nécessité un rabaissement complémentaire de la nappe par drainage en partie pour augmenter la désalinisation de surface et limiter l’engorgement des sols. Néanmoins, ces territoires restent caractérisés par des nappes proches de la surface. En conséquence les profils hydriques vont être gouvernés par les conditions météorologiques y compris l'évapotranspiration, la pluviométrie, mais également par les remontées capillaires issues d'une nappe salée. D'autre par la nature argileuse des sols et ses propriétés de retrait conditionnent énormément le fonctionnement hydrodynamique et les évolutions de structure.La première partie du travail a été de suivre les évolutions des profils hydriques et de salinité en parcelles non drainées (prairies) et en parcelles drainées (Maïs, Blé, Tournesol). Ces suivis ont été complétés par les mesures des niveaux de nappes et par des mesures tensiométriques via des bougies poreuses implantées à différentes profondeurs. L'objectif final a été de calculer et modéliser les profils de réserve utile (RU) et de RU "résiduelle" utilisable par les plantes. Dans ces systèmes alimentés par les remontées capillaires, le réseau racinaire puise l'eau dans la zone non saturée de surface (vadose) puis dans la zone saturée sous-jacente. La teneur en eau caractéristique de l'interface zone non saturée - zone saturée a été déterminée par analogie entre les chemins d'état de la matrice argileuse le long de sa courbe de retrait et du sol le long de sa courbe de compaction. Les profils de RU résiduelle utilisable par les plantes ont été calculés à partir des profils de teneurs en eau puis comparés aux profils de RU obtenus via les données de station météorologique. Ces profils de RU résiduelle ont pu être écrits sous forme d'équation polynomiale du second degré puis modélisés. Dans cet environnement alimenté par les remontées capillaires, ces profils de RU résiduelles peuvent être modélisés à partir d'un paramètre facilement mesurable en surface qui prend en compte la structure du sol et les conditions météorologique : soit la teneur en eau à 10 cm de profondeur. Cette modélisation reste suffisamment réaliste pour être utilisée comme un outil prédictif face à la pédodiversité et/ou les rendements de culture.A ce travail s'ajoute deux études préliminaires : - les mesures des conductivités thermiques effectives de ces sols par la méthode du fil chaud et leurs modélisations dans les systèmes biphasés : eau - argile et air - argile, mais également pour les systèmes triphasés non saturés : eau - air - argile. Les perspectives sont la modélisation des transferts thermiques et hydriques dans le sol à partir de la surface, - et l'élaboration d'un protocole d'imprégnation-polymérisation des sols argileux humides par des résines de type HEMA. Cette imprégnation permet d'envisager la confection de lames minces dans le matériau argileux induré avec conservation de sa structure initiale humide. Les perspectives sont la pétrographie quantitative à l'interface racine - sol le long de profils verticaux dans les environnements argileux à degrés de saturation et structure évolutives
The coastal marshlands are territories generally reclaimed on primary fluvio-marine sediments. They result from hydraulic managements and/or polderization which may date from the Middle Ages. Historically these hydraulic managements were built for goals of wholesomeness, breeding and farming. They isolate two territories: the dried marshes and the wet marshes. For the intensive cereal crops the slow drying caused by land reclamation was recently improved by the drainage, in part for increase the depth of desalinization and decrease waterlogging. Nevertheless, these territories remain characterized by shallow ground water of initial salt water. Consequently, the hydric profiles are governed by the meteoric conditions including the Evapotranspiration, the rainfall, but also the capillarity rises from the salt groundwater. Moreover, the clay dominated nature of the soils and their drastic shrinkage properties govern the hydrodynamic functioning and the soil structure behavior.The first part of the work was the monitoring of the water content and salinity profiles in drained cereal crops and in undrained grasslands. These measurements have been completed by the ground water level and tensiometric monitoring. The final goal was the calculation and modeling of the available water capacity (AWC) and plant available water (PAW) profiles. In these systems mainly supplied by the capillarity rises, the root network gets water in the subsurface vadose zone and then in the deeper saturated groundwater zone. The water content characteristic of the interface between the vadose and saturated zone was determined by comparison between the clay material state paths along its shrinkage curve and along its compaction curve. The PAW profiles were calculated from the water content profiles and then compared to the AWC profiles. The PAW profiles have been equated as polynomial second degree equations. In these shallow groundwater environments the PAW profiles have been modeled taking into account an easy measurable surface parameter which includes the soil structure behavior and the meteoric conditions: i.e. the water content measured at 10 cm depth. The PAW modelling remains sufficiently realistic to be used as a tool for farming management. Two preliminary studies were added to this work: - the measurement of effective thermal conductivity of the clayey soils by the transient hot wire method, and the modeling of the effective thermal conductivity of biphasic air-clay and water-clay media, but also triphasic unsaturated air-water-clay media. The prospect is the modeling of thermal and hydric transfer from the surface to the depth. - and the elaboration of a protocol of impregnation - hardening for wet clay dominated soils by HEMA resins. This impregnation allows the making of thin sections in these clay materials with conservation of their initial wet structures. The prospective is the quantitative petrography at the root - clay matrix interface along vertical profiles in clayey soils at different degrees of saturation and different structures

Wildfires are a growing threat, especially in Mediterranean climate areas during periods of drought. Wildfire research community continues to investigate propagation mechanisms on a large scale considering the thermal and fluid mechanics effects, or the main fire emissions (CO, CO2, H2O, H2, CH4). However, research on the effect of abiotic stresses on the plant emission during wildfires remains lacking, despite the fact that Mediterranean are considered important BVOC emitting and storing species. This article addresses the effect of combined hydric and thermal stresses on the volatile’s emission behaviours of two important Mediterranean shrub species; Rosmarinus officinalis and Cistus albidus that are largely consumed in wildfires. Different levels of hydric stress were applied on plants of the two species in a greenhouse of the EBI laboratories of the University of Poitiers. Thermal stress was executed by placing the water stressed plants inside a hermetic enclosure equipped with a radiant panel of maximal radiant heat flux of 84kW.m-2 and a fire-resistant glazed window for visualisation. The gaseous emissions of the plants under thermal stresses were collected and analysed by two complementary devices: an instantaneous gas analyser for CO, CO2, H2 and CH4, and adsorbent tubes by using the techniques of adsorption and desorption (by pyrolysis) for emission collection and analyses, respectively. Simultaneous Py/GC-MS experiments were realised at IC2MP on a foliar scale of the water stressed plants in order to gain more control and precision in emission analyses. The heating tests showed a good reproducibility for pyrolyses of leaf samples and interesting variations between the monoterpene emissions of stressed and unstressed plants. At plant scale, number of tests for each plant species at a given hydric stress level were insufficient to give trends and strong results because of some imposed technical problems and the constraints of public health crisis. However, these tests allowed us to adapt experimental protocols and devices for further testing such as: plant location and fixation, heat flux ramp, sampling location, use of adsorbent tubes, hydric stress duration and normalisation of measured concentrations according to the plant size.

Retained Strength has been used to characterize the damage incurred by brittle materials when exposed to a thermal shock or to a sequence of thermal shocks. While it is a valid measure to qualitatively rank materials in a simplistic way, it cannot be used in any quantitative sense since it depends upon the specific thermal shock conditions and upon the type of test used to measure it. Given the current state of knowledge about fracture of brittle materials, retained strength should be considered as an artifact of a time when little was understood about fracture of brittle materials. When the residual strength of a ceramic is measured by mechanical tests subsequent to the exposure of a ceramic to a thermal shock, the isothermal test condtions must produce a stress field that is consistent with the stresses produced by the thermal shock. This paper describes the theoretical basis for retained strength and presents experimental data to show that retained strength measured from the isothermal tests cannot be used in general as an accurate measure of the thermal damage.

Buildings are responsible for a large portion of the total energy consumption, and have a heavy environmental impact. Wood is one of the most used bio-based building materials, as it helps reducing the environmental footprint of the construction sector. Spruce wood is widely available in France and therefore massively used in buildings. It has interesting thermal and acoustic insulation performances and a good hydric regulation property. Spruce wood microstructure is highly heterogeneous and multiphasic, which makes it harder to apprehend. On the other hand, sorption hysteresis phenomenon is responsible for the moisture accumulation in porous building materials. It is often neglected in hygrothermal transfers modelling, which leads to incorrect water content values. The aim of this work is to investigate the influence of the sorption hysteresis phenomenon on the hydric transfers of spruce wood. The heterogeneity of the microstructure is also considered through 3D tomographic reconstructions included in the modelling.